So Tree of Perdition is one of the best threats you can include
While I think a Commander like Sidar Jafar of Zhalfir is a little more constricting in terms of deck design compared to a Commander like Y'shtola, Night's Blessed, I do really like all the intricate synergies you can include in a Sidar deck You also have multiple ways to protect your board state from sweeper effects, like Knights' Charge and Guardian of Faith
(When a creature with undying dies, if it had no +1/+1 counters on it, return it to the battlefield under its owner's control with a +1/+1 counter on it.) Whenever a Human deals damage to you, destroy it
Cantrips Players new to card games like Magic: The Gathering are often confused why cards that just draw a replacement are valued so highly
Bigger Ninjas are harder to block favorably, and discounting some ninjutsu abilities helps, too, but this is going to have to fight for its spot even in Ninja-themed Constructed decks